The invention concerns a rotation apparatus for shafts of rotating machines, especially for turbine shafts, including a hydrostatic motor with an overriding clutch as well as an auxiliary drive mechanism for breaking the inertia as well as for turning the shaft.
When rotating machines are shut down, and especially in the case of turbines that are still heated up after operating, it is necessary to keep the shaft train rotating at a continuous rotary motion by means of a shaft-turning device in order to avoid any bending of the shaft. Furthermore, the starting of large-sized turbines poses the problem of breaking the inertia of the shaft and to set the rotor in motion without any jerking.
In the case of known turning systems the shaft trains of the turbines are usually driven by means of an electro-motor with a turbocoupling, a reduction gear and/or an overriding clutch. These known arrangements require the additional installation of an emergency shaft-turning device with a piston ratchet finger to provide for the possibility of a break-down of the drive unit, especially of the overriding clutch. This ratchet finger can be actuated either mechanically or hydraulically.
There are also known turning systems where a belt possessing a high coefficient of friction is wound around the shaft to be set in motion and is pulled by way of a linkage upon the lifting of a piston by a properly applied oil pressure in such manner that the shaft can be moved from its position of rest (see British Pat. No. 10,24,895).
However, such arrangement will solely permit the breaking of the inertia and possibly a momentary acceleration of the shaft but an extensive turning operation is not possible. Furthermore, since this rotation apparatus must make allowance for the maximum possible starting moment, the engineering expenditures will be high.
Still other shaft-turning arrangements have been in use where a hydrostatic motor is placed directly onto the turbine shaft, driving the shaft by way of a shiftable coupling or an overriding clutch, with the additional use of a pressure intensifier, designed in the form of a differential piston, to attain the high starting moment necessary to break the inertia of the shaft (see published German application 19 56 178).
It is the main disadvantage of the known arrangements that the use of electro-motors causes the rotation apparatus to start very abruptly making it necessary to employ an elastic or turbo-coupling. Furthermore, a very large step-down ratio requires the use of a multistage gearing with a disadvantageous effect on the size of the housing as well as on the overall length of the shaft train.
It is an object of the invention to provide a rotation apparatus where the turbine shaft is driven by a hydrostatic motor in such manner that an axial expansion of the turbine shaft will not influence adversely the drive motor and where the hydrostatic drive can be utilized for breaking the inertia as well as for a continuous rotation and at reduced r.p.m.